AMPA-binding human GluR3 receptors

ABSTRACT

Described herein are isolated polynucleotides which code for a family of AMPA-type human CNS receptors. The receptors are characterized structurally and the construction and use of cell lines expressing these receptors are disclosed.

FIELD OF THE INVENTION

[0001] This invention is concerned with applications of recombinant DNA technology in the field of neurobiology. More particularly, the invention relates to the cloning and expression of DNA coding for excitatory amino acid (EAA) receptors, especially human EAA receptors.

BACKGROUND TO THE INVENTION

[0002] In the mammalian central nervous system (CNS), the transmission of nerve impulses is controlled by the interaction between a neurotransmitter substance released by the “sending” neuron which then binds to a surface receptor on the “receiving” neuron to cause excitation thereof. L-glutamate is the most abundant neurotransmitter in the CNS, and mediates the major excitatory pathway in vertebrates. Glutamate is therefore referred to as an excitatory amino acid (EAA) and the receptors which respond to it are variously referred to as glutamate receptors, or more commonly as EAA receptors.

[0003] Using tissues isolated from mammalian brain, and various synthetic EAA receptor agonists, knowledge of EAA receptor pharmacology has been refined somewhat. Members of the EAA receptor family are now grouped into three main types based on differential binding to such agonists. One type of EAA receptor, which in addition to glutamate also binds the agonist NMDA (N-methyl-D-aspartate), is referred to as the NMDA type of EAA receptor. Two other glutamate-binding types of EAA receptor, which do not bind NMDA, are named according to their preference for binding with two other EAA receptor agonists, namely AMPA (alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate), and kainate. Particularly, receptors which bind glutamate but not NMDA, and which bind with greater affinity to kainate than to AMPA, are referred to as kainate type EAA receptors. Similarly, those EAA receptors which bind glutamate but not NMDA, and which bind AMPA with greater affinity than kainate are referred to as AMPA type EAA receptors.

[0004] The glutamate-binding EAA receptor family is of great physiological and medical importance. Glutamate is involved in many aspects of long-term potentiation (learning and memory), in the development of synaptic plasticity, in epileptic seizures, in neuronal damage caused by ischemia following stroke or other hypoxic events, as well as in other forms of neurodegenerative processes. However, the development of therapeutics which modulate these processes has been very difficult, due to the lack of any homogeneous source of receptor material with which to discover selectively binding drug molecules, which interact specifically at the interface of the EAA receptor. The brain derived tissues currently used to screen candidate drugs are heterogeneous receptor sources, possessing on their surface many receptor types which interfere with studies of the EAA receptor/ligand interface of interest. The search for human therapeutics is further complicated by the limited availability of brain tissue of human origin. It would therefore be desirable to obtain cells that are genetically engineered to produce only the receptor of interest. With cell lines expressing cloned receptor genes, a substrate which is homogeneous for the desired receptor is provided, for drug screening programs.

[0005] Very recently, genes encoding substituent polypeptides of EAA receptors from non-human sources, principally rat, have been discovered. Hollmann et al., Nature 342: 643, 1989 described the isolation from rat of a gene referred to originally as GluR-K1 (but now called simply GluR1). This gene encodes a member of the rat EAA receptor family, and was originally suspected as being of the kainate type. Subsequent studies by Keinanen et al., Science 249: 556, 1990, showed, again in rat, that a gene called GluR-A, which was in fact identical to the previously isolated GluR1, in fact encodes a receptor not of the kainate type, but rather of the AMPA type. These two groups of researchers have since reported as many as five related genes isolated from rat sources. Boulter et al., Science 249: 1033, 1990, revealed that, in addition to GluR1, the rat contained 3 other related genes, which they called GluR2, GluR3, and GluR4, and Bettler et al., Neuron 5: 583. 1990 described GluR5. Keinanen et al., supra, described genes called GluRA, GluFI-B, GluR-C and GluR-D which correspond precisely to GluR1, GluR2, GluR3 and GluR4 respectively. Sommer et at., Science 249: 1580, 1990 also showed, for GluR-A, GluR-B, GluR-C and GluR-D two alternatively spliced forms for each gene. These authors, as well as Monyer et al., Neuron 6: 799, 1991 were able to show that the differently spliced versions of these genes were differentially expressed in the rat brain. In addition to the isolation of these AMPA receptor genes, several studies have more recently attempted to determine the ion-gating properties of different mixtures of the known receptors (Nakanishi et al., Neuron 5: 569, 1990; Hollmann et al., Science 252: 851, 1991; Verdoorn et al., Science 252: 1715, 1991; and see WO 91/06648).

[0006] There has emerged from these molecular cloning advances a better understanding of the structural features of EAA receptors and their subunits, as they exist in the rat brain. According to the current model of EAA receptor structure, each is heteromeric in structure, consisting of individual membraneanchored subunits, each having four transmembrane regions, and extracellular domains that dictate ligand binding properties to some extent and contribute to the ion-gating function served by the receptor complex. Keinanen et al, supra, have shown for example that each subunit of the rat GluR receptor, including those designated GluR-A, GluR-B, GluR-C and GluR-D, display cation channel activity gated by glutamate, by AMPA and by kainate, in their unitary state. When expressed in combination however, for example GluR-A in combination with GluR-B, gated ion channels with notably larger currents are produced by the host mammalian cells.

[0007] In the search for therapeutics useful to treat CNS disorders in humans, it is highly desirable of course to provide a screen for candidate compounds that is more representative of the human situation than is possible with the rat receptors isolated to date. It is particularly desirable to provide cloned genes coding for human receptors, and cell lines expressing those genes, in order to generate a proper screen for human therapeutic compounds. These, accordingly, are objects of the present invention.

SUMMARY OF THE INVENTION

[0008] The present invention provides a family of isolated polynucleotides that code for AMPA-binding human EAA receptors. By providing polynucleotides that code specifically for CNS receptors native to humans, the present invention provides means for evaluating the human nervous system, and particularly for assessing potentially therapeutic interactions between the AMPA-binding human EAA receptors and selected natural and synthetic ligands.

[0009] In one of its aspects, the present invention provides an isolated polynucleotide comprising nucleic acids arranged in a sequence that codes for an EAA receptor belonging to the human GluR3 family. Alternatively, the polynucleotide may code for an AMPA-binding fragment of a human GluR3 receptor, or for an AMPA-binding variant of a human GluR3 receptor. According to one embodiment of the present invention, the isolated polynucleotide encodes a receptor comprising amino acids arranged in the sequence herein specified with reference to FIGS. 1A-1E (SEQ ID NOs. 1 and 2), and referred to as the human GluR3A receptor. According to another embodiment of the invention, the polynucleotide encodes a variant of the human GluR3A receptor, which variant has the amino acid sequence herein specified with reference to FIGS. 3A-3F (SEQ ID NOs. 3 and 4) and is herein referred to as the human GluR3B receptor. In various specific embodiments of the present invention, the polynucleotide consists of DNA e.g. cDNA, or of RNA e.g. messenger RNA. In other embodiments of the present invention, the polynucleotide may be coupled to a reporter molecule, such as a radioactive label, for use in autoradiographic studies of human GluR3 receptor tissue distribution. In further embodiments of the present invention, fragments of the polynucleotides of the invention, including radiolabelled versions thereof, may be employed either as probes for detection of glutamate receptor-encoding polynucleotides, as primers appropriate for amplifying such polynucleotides present in a biological specimen, or as templates for expression of a GluR3 receptor or an AMPA-binding fragments or variant thereof.

[0010] According to another aspect of the present invention, there is provided a cellular host having incorporated therein a polynucleotide of the present invention. In embodiments of the present invention, the polynucleotide is a DNA molecule and is incorporated for expression and secretion in the cellular host, to yield a functional, membrane-bound human GluR3 receptor. In other embodiments of the present invention, the polynucleotide is an RNA molecule which is incorporated in the cellular host to yield the human GluR3 receptor as a functional, membrane-bound product of translation.

[0011] According to another aspect of the invention, there is provided a process for obtaining a substantially homogeneous source of a human EAA receptor useful for performing ligand binding assays, which comprises the steps of culturing a genetically engineered cellular host of the invention, and then recovering the cultured cells. Optionally, the cultured cells may be treated to obtain membrane preparations thereof, for use in the ligand binding assays.

[0012] According to another aspect of the present invention, there is provided a method for assaying interaction between a test ligand and a human EAA receptor, comprising the steps of incubating the test ligand under appropriate conditions with a human GluR3 receptor source, i.e., a cellular host of the invention or a membrane preparation derived therefrom, and then determining between the substance and the receptor source.

[0013] These and other aspects of the invention are now described in greater detail with reference to the accompanying drawings, in which:

BRIEF REFERENCE TO THE DRAWINGS

[0014] FIGS. 1A-1E provide a DNA sequence (SEQ ID NO:1) coding for the human GluR3A receptor, and the amino acid sequence (SEQ ID NO: 2) thereof;

[0015]FIG. 2 depicts the strategy employed in cloning the human GluR3A receptor-encoding DNA illustrated in FIGS. 1A-1E;

[0016] FIGS. 3A-3F provide a DNA sequence (SEQ ID NO: 3) coding for the human GluR3B receptor, and the amino acid sequence (SEQ ID NO: 4) thereof;

[0017]FIG. 4 depicts the strategy employed in cloning the human GluR3A receptor-encoding DNA illustrated in FIGS. 3A-3F;

[0018]FIG. 5 depicts the strategy employed in generating recombinant DNA expression constructs incorporating the receptor-encoding DNA;

[0019]FIG. 6 provides the amino acid sequence of the human GluR3A receptor (SEQ ID NO: 5) and the human GluR3B receptor (SEQ ID NO: 6) in a region of dissimilarity; and

[0020]FIG. 7 illustrates the AMPA-binding property of the human GluR3A receptor.

DETAILED DESCRIPTION OF THE INVENTION AND ITS PREFERRED EMBODIMENTS

[0021] The invention relates to human CNS receptors of the AMPA-binding type, and provides isolated polynucleotides that code for such receptors. The term “isolated” is used herein with reference to intact polynucleotides that are generally less than about 4,000 nucleotides in length and which are otherwise isolated from DNA coding for other human proteins.

[0022] In the present context, human CNS receptors of the AMPA-binding type exhibit a characteristic ligand binding profile, which reveals glutamate binding and relative greater affinity for binding AMPA than for other binding other CNS receptor ligands such as kainate, glutamate and their closely related analogues.

[0023] In the present specification, an AMPA-binding receptor is said to be “functional” if a cellular host producing it exhibits de novo channel activity when exposed appropriately to AMPA, as determined by the established electrophysiological assays described for example by Hollman et al. supra, or by any other assay appropriate for detecting conductance across a cell membrane.

[0024] Members of the human GluR3 family of the invention possess structural features characteristic of the EAA receptors in general, including extracellular N- and C-terminal regions, as well as four internal hydrophobic domains which serve to anchor the receptor within the cell surface membrane. The GluR3A member of the human GluR3 family is a protein characterized structurally as a single polypeptide chain that is produced initially in precursor form bearing a 22 amino acid residue N-terminal signal peptide, and is transported to the cell surface in mature form, lacking the signal peptide and consisting of 866 amino acids arranged in the sequence illustrated, by single letter code, in FIGS. 1A-1E and SEQ ID NOs. 1 and 2. Unless otherwise stated, the term human GluR3A receptor refers to the mature form of the receptor, and amino acid residues of the individual human GluR3 receptors are accordingly numbered with reference to the mature protein sequence. With respect to structural domains of the receptor, hydropathy analysis reveals four putative transmembrane domains, one spanning residues 527-546 inclusive (TM-1), another spanning residues 575-593 (TM-2), a third spanning residues 604-622 (TM-3) and the fourth spanning residues 796-816 (TM-4). Based on this assignment, it is likely that the human GluR3A receptor structure, in its natural membrane-bound form, consists of a 526 amino acid N-terminal extracellular domain, followed by a hydrophobic region containing four transmembrane domains and an extracellular, 50 amino acid C-terminal domain.

[0025] As shown in FIGS. 3A-3F and SEQ ID NOs. 3 and 4, a structurally related variant of the human GluR3A receptor that occurs naturally in human brain tissue has also been identified, and is designated herein as the human GluR3B receptor. Like GluR3A, the GluR3B receptor is also 866 amino acids in length in its mature, membrane-bound form, and initially bears a signal peptide identical to that borne on the GluR3A receptor. Four transmembrane domains are also apparent from the GluR3B sequence, and indicate that these domains lie in the same amino acid regions just indicated in connection with the GluR3A receptor.

[0026] With respect to primary structure, the human GluR3B receptor differs from the GluR3A receptor in 36 amino acid region separating transmembrane domains TM-3 and TM-4, i.e. residues 748-783. For comparison, the sequences of GluR3A and GluR3B in this region are compared in FIG. 6 and are also shown in SEQ ID NOs. 5 and 6.

[0027] Binding assays performed with various ligands, and with membrane preparations derived from mammalian cells engineered genetically to produce the human GluR3 receptors in membrane-bound form indicate that both human GluR3A and human GluR3B bind selectively to AMPA, relative particularly to kainate and NMDA. This feature, coupled with the medically significant connection between AMPA-type receptors and neurological disorders and disease indicate that the present receptors, as well as AMPA-binding fragments and variants thereof, will serve as valuable tools in the screening and discovery of ligands useful to modulate in vivo interactions between such receptors and their natural ligand, glutamate. Thus, a key aspect of the present invention resides in the construction of cells that are engineered genetically to produce human GluR3 receptor, to serve as a ready and homogeneous source of receptor for use in in vitro ligand binding and/or channel activation assays.

[0028] For use in the ligand binding assays, it is desirable to construct by application of genetic engineering techniques a mammalian cell that produces a human GluR3 receptor as a heterologous and membrane-bound product. According to one embodiment of the invention, the construction of such engineered cells is achieved by introducing into a selected host cell a recombinant DNA construct in which DNA coding for a secretable form of the desired human GluR3 receptor, i.e., a form bearing its native signal peptide or a functional, heterologous equivalent thereof, is linked operably with expression controlling elements that are functional in the selected host to drive expression of the receptor-encoding DNA, and thus elaborate the desired human GluR3 receptor protein. Such cells are herein characterized as having the receptor-encoding DNA incorporated “expressibly” therein. The receptor-encoding DNA is referred to as “heterologous” with respect to the particular cellular host if such DNA is not naturally found in the particular host. The particular cell type selected to serve as host for production of the human GluR3 receptor can be any of several cell types currently available in the art, but should not of course be a cell type that in its natural state elaborates a surface receptor that can bind excitatory amino acids, and so confuse the assay results sought from the engineered cell tine. Generally, such problems are avoided by selecting as host a non-neuronal cell type, and can further be avoided using non-human cell lines, as is conventional. It will be appreciated that neuronal- and human-type cells may nevertheless serve as expression hosts, provided that “background” binding to the test ligand is accounted for in the assay results.

[0029] According to one embodiment of the present invention, the cell line selected to serve as host for human GluR3 receptor production is a mammalian cell. Several types of such cell lines are currently available for genetic engineering work, and these include the chinese hamster ovary (CHO) cells for example of K1 lineage (ATCC CCL 61) including the Pro5 variant (ATCC CRL 1281); the fibroblast-like cells derived from SV40-transformed African Green monkey kidney of the CV-1 lineage (ATCC CCL 70), of the COS-1 lineage (ATCC CRL 1650) and of the COS-7 lineage (ATCC CRL 1651); murine L-cells, murine 3T3 cells (ATCC CRL 1658), murine C127 cells, human embryonic kidney cells of the 293 lineage (ATCC CRL 1573), human carcinoma cells including those of the HeLa lineage (ATCC CCL 2), and neuroblastoma cells of the lines IMR-32 (ATCC CCL 127), SK-N-MC (ATCC HTB 10) and SK-N-SH (ATCC HTB 11).

[0030] A variety of gene expression systems have been adapted for use with these hosts and are now commercially available, and any one of these systems can be selected to drive expression of the human GluR3 receptor-encoding DNA. These systems, available typically in the form of plasmidic vectors, incorporate expression cassettes the functional components of which include DNA constituting expression controlling sequences, which are host-recognized and enable expression of the receptor-encoding DNA when linked 5′ thereof. The systems further incorporate DNA sequences which terminate expression when linked 3′ of the receptor-encoding region. Thus, for expression in the selected mammalian cell-host, there is generated a recombinant DNA expression construct in which DNA coding for a secretable form of the receptor is linked with expression controlling DNA sequences recognized by the host, and which include a region 5′ of the receptor-encoding DNA to drive expression, and a 3′ region to terminate expression. The plasmidic vector harbouring the recombinant DNA expression construct typically incorporates such other functional components as an origin of replication, usually virally-derived, to permit replication of the plasmid in the expression host and desirably also for plasmid amplification in a bacterial host, such as E. coli. To provide a marker enabling selection of stably transformed recombinant cells, the vector will also incorporate a gene conferring some survival advantage on the transformants, such as a gene coding for neomycin resistance in which case the transformants are plated in medium supplemented with neomycin.

[0031] Included among the various recombinant DNA expression systems that can be used to achieve mammalian cell expression of the receptor-encoding DNA are those that exploit promoters of viruses that infect mammalian cells, such as the promoter from the cytomegalovirus (CMV), the Rous sarcoma virus (RSV), simian virus (SV40), murine mammary tumor virus (MMTV) and others. Also useful to drive expression are promoters such as the LTR of retroviruses, insect cell promoters such as those regulated by temperature, and isolated from Drosophila, as well as mammalian gene promoters such as those regulated by heavy metals i.e. the metalothionein gene promoter, and other steroid-inducible promoters.

[0032] For incorporation into the recombinant DNA expression vector, DNA coding for a selected human GluR3 receptor, e.g. the human GluR3A receptor, the human GluR3B receptor or an AMPA-binding fragment or variant thereof, can be obtained by applying selected techniques of gene isolation or gene synthesis. As described in more detail in the examples herein, the human GluR3A receptor and the human GluR3B receptor are encoded within the genome of human brain tissue, and can therefore be obtained from human DNA libraries by careful application of conventional gene isolation and cloning techniques. This typically will entail extraction of total messenger RNA from a fresh source of human brain tissue, preferably cerebellum or hippocampus tissue, followed by conversion of message to cDNA and formation of a library in for example a bacterial plasmid, more typically a bacteriophage. Such bacteriophage harbouring fragments of the human DNA are typically grown by plating on a lawn of susceptible E. coli bacteria, such that individual phage plaques or colonies can be isolated. The DNA carried by the phage colony is then typically immobilized on a nitrocellulose or nylon-based hybridization membrane, and then hybridized, under carefully controlled conditions, to a radioactively (or otherwise) labelled oligonucleotide probe of appropriate sequence to identify the particular phage colony carrying receptor-encoding DNA or fragment thereof. Typically, the gene or a portion thereof so identified is subcloned into a plasmidic vector for nucleic acid sequence analysis.

[0033] In a specific embodiment of the invention, the selected GluR3 receptor is encoded by the DNA sequence illustrated in FIGS. 1A-1E and SEQ ID NO: 1, for the GluR3A receptor, and by the DNA sequence illustrated in FIGS. 3A-3F and SEQ ID NO:3, for the GluR3B receptor. In an obvious alternative, the DNA sequences coding for the selected receptor may be a synonymous codon equivalent of the illustrated DNA sequences.

[0034] The illustrated DNA sequences constitute cDNA sequences identified in human brain cDNA libraries in the manner exemplified herein. Having herein provided the nucleotide sequence of various members of the human GluR3 receptor family, however, it will be appreciated that polynucleotides encoding the receptors can be obtained by other routes. Automated techniques of gene synthesis and/or amplification can be performed to generate DNA coding therefor. Because of the length of the human GluR3 receptor-encoding DNA, application of automated synthesis may require staged gene construction, in which regions of the gene up to about 300 nucleotides in length are synthesized individually and then ligated in correct succession by overhang complementarity for final assembly. Individually synthesized gene regions can be amplified prior to assembly, using established polymerase chain reaction (PCR) technology.

[0035] The application of automated gene synthesis techniques provides an opportunity for generating polynucleotides that encode variants of naturally occurring human GluR3A and GluR3B receptors. It will be appreciated, for example, that polynucleotides coding for the human GluR3 receptors herein described can be generated by substituting synonymous codons for those represented in the naturally occurring polynucleotide sequences herein identified. In addition, polynucleotides coding for human GluR3 receptor variants can be generated which for example incorporate one or more e.g. 1-10, single amino acid substitutions, deletions or additions. Since it will for the most part be desirable to retain the natural ligand binding profile of the receptor for screening purposes, it is desirable to limit amino acid substitutions, for example to the so-called conservative replacements in which amino acids of like charge are substituted, and to limit substitutions to those sites less critical for receptor activity e.g. within about the first 20 N-terminal residues of the mature receptor, and such other regions as are elucidated upon receptor domain mapping.

[0036] With appropriate template DNA in hand, the technique of PCR amplification may also be used to directly generate all or part of the final gene. In this case, primers are synthesized which will prime the PCR amplification of the final product, either in one piece, or in several pieces that may be ligated together. This may be via step-wise ligation of blunt ended, amplified DNA fragments, or preferentially via step-wise ligation of fragments containing naturally occurring restriction endonuclease sites. In this application, it is possible to use either cDNA or genomic DNA as the template for the PCR amplification. In the former case, the cDNA template can be obtained from commercially available or self-constructed cDNA libraries of various human brain tissues, including hippocampus and cerebellum.

[0037] Once obtained, the receptor-encoding DNA is incorporated for expression into any suitable expression vector, and host cells are transfected therewith using conventional procedures, such as DNA-mediated transformation, electroporation, or particle gun transformation. Expression vectors may be selected to provide transformed cell lines that express the receptor-encoding DNA either transiently or in a stable manner. For transient expression, host cells are typically transformed with an expression vector harbouring an origin of replication functional in a mammalian cell. For stable expression, such replication origins are unnecessary, but the vectors will typically harbour a gene coding for a product that confers on the transformants a survival advantage, to enable their selection. Genes coding for such selectable markers include the E. coli gpt gene which confers resistance to mycophenolic acid, the neo gene from transposon Tn5 which confers resistance to the antibiotic G418 and to neomycin, the dhfr sequence from murine cells or E. coli which changes the phenotype of DHFR− cells into DHFR+ cells, and the tk gene of herpes simplex virus, which makes TK− cells phenotypically TK+ cells. Both transient expression and stable expression can provide transformed cell lines, and membrane preparations derived therefrom, for use in ligand screening assays.

[0038] For use in screening assays, cells transiently expressing the receptor-encoding DNA can be stored frozen for later use, but because the rapid rate of plasmid replication will lead ultimately to cell death, usually in a few days, the transformed cells should be used as soon as possible. Such assays may be performed either with intact cells, or with membrane preparations derived from such cells. The membrane preparations typically provide a more convenient substrate for the ligand binding experiments, and are therefore preferred as binding substrates. To prepare membrane preparations for screening purposes, i.e., ligand binding experiments, frozen intact cells are homogenized while in cold water suspension and a membrane pellet is collected after centrifugation. The pellet is then washed in cold water, and dialyzed to remove endogenous EAA ligands such as glutamate, that would otherwise compete for binding in the assays. The dialyzed membranes may then be used as such, or after storage in lyophilized form, in the ligand binding assays. Alternatively, intact, fresh cells harvested about two days after transient transfection or after about the same period following fresh plating of stably transfected cells, can be used for ligand binding assays by the same methods as used for membrane preparations. When cells are used, the cells must be harvested by more gentle centrifugation so as not to damage them, and all washing must be done in a buffered medium, for example in phosphate-buffered saline, to avoid osmotic shock and rupture of the cells.

[0039] The binding of a substance, i.e., a candidate ligand, to a human GluR3 receptor of the invention is evaluated typically using a predetermined amount of cell-derived membrane (measured for example by protein determination), generally from about 25 ug to 100 ug. Generally, competitive binding assays will be useful to evaluate the affinity of a test compound relative to AMPA. This competitive binding assay can be performed by incubating the membrane preparation with radiolabelled AMPA, for example [3H]-AMPA, in the presence of unlabelled test compound added at varying concentrations. Following incubation, either displaced or bound radiolabelled AMPA can be recovered and measured, to determine the relative binding affinities of the test compound and AMPA for the particular receptor used as substrate. In this way, the affinities of various compounds for the AMPA-binding human EAA receptors can be measured. Alternatively, a radiolabelled analogue of glutamate may be employed in place of radiolabelled AMPA, as competing ligand.

[0040] As an alternative to using cells that express receptor-encoding DNA, ligand characterization may also be performed using cells for example Xenopus oocytes, that yield functional membrane-bound receptor following introduction by injection either of receptor-encoding messenger RNA into the oocyte cytoplasm, or of receptor-encoding DNA into the oocyte nucleus. To generate the messenger RNA of cytoplasmic delivery, the receptor-encoding DNA is typically subcloned first into a plasmidic vector adjacent a suitable promoter region, such as the T3 or T7 bacteriophage promoters, to enable transcription into RNA message. RNA is then transcribed from the inserted gene in vitro, collected and then injected into Xenopus oocytes. Following the injection of nL volumes of an RNA solution, the oocytes are left to incubate for up to several days, and are then tested for the ability to respond to a particular ligand molecule supplied in a bathing solution. Since functional EAA receptors act in part by operating a membrane channel through which ions may selectively pass, the functioning of the receptor in response to a particular ligand molecule in the bathing solution may typically be measured as an electrical current utilizing microelectrodes inserted into the cell, in the established manner.

[0041] In addition to using the receptor-encoding DNA to construct cell lines useful for ligand screening, expression of the DNA can, according to another aspect of the invention, be performed to produce fragments of the receptor in soluble form, for structure investigation, to raise antibodies and for other experimental uses. It is expected that the portion of the human GluR3 receptor responsible for AMPA-binding resides on the outside of the cell, i.e., is extracellular. It is therefore desirable in the first instance to facilitate the characterization of the receptor-ligand interaction by providing this extracellular ligand-binding domain in quantity and in isolated form, i.e., free from the remainder of the receptor. To accomplish this, the full-length human GluR receptor-encoding DNA may be modified by site-directed mutagenesis, so as to introduce a translational stop codon into the extracellular N-terminal region, immediately before the sequence encoding the first transmembrane domain (TM1), i.e., before residue 527 as shown in FIGS. 1A-1E and SEQ ID NOs. 1 and 2. Since there will no longer be produced any transmembrane domain(s) to “anchor” the receptor into the membrane, expression of the modified gene will result in the secretion, in soluble form, of only the extracellular ligand-binding domain. Standard ligand-binding assays may then be performed to ascertain the degree of binding of a candidate compound to the extracellular domain so produced. It may of course be necessary, using site-directed mutagenesis, to produce several different versions of the extracellular regions, in order to optimize the degree of ligand binding to the isolated domains.

[0042] Alternatively, it may be desirable to produce an extracellular domain of the receptor which is not derived from the amino-terminus of the mature protein, but rather from the carboxy-terminus instead, for example domains immediately following the fourth transmembrane domain (TM4), i.e., residing between amino acid residues 817-866 inclusive (FIGS. 1A-1E and SEQ ID NOs. 1 and 2). In this case, site-directed mutagenesis and/or PCR-based amplification techniques may readily be used to provide a defined fragment of the gene encoding the receptor domain of interest. Such a DNA sequence may be used to direct the expression of the desired receptor fragment, either intracellularly, or in secreted fashion, provided that the DNA encoding the gene fragment is inserted adjacent to a translation start codon provided by the expression vector, and that the required translation reading frame is carefully conserved.

[0043] It will be appreciated that the production of such AMPA-binding fragments of a GluR3 receptor may be accomplished in a variety of host cells. Mammalian cells such as CHO cells may be used for this purpose, the expression typically being driven by an expression promoter capable of high-level expression, for example the CMV (cytomegalovirus) promoter. Alternately, non-mammalian cells, such as insect Sf9 (Spodoptera frugiperda) cells may be used, with the expression typically being driven by expression promoters of the baculovirus, for example the strong, late polyhedrin protein promoter. Filamentous fungal expression systems may also be used to secrete large quantities of such extracellular domains of the EAA receptor. Aspergillus nidulans, for example, with the expression being driven by the alcA promoter, would constitute such an acceptable system. In addition to such expression hosts, it will be further appreciated that any prokaryotic or other eukaryotic expression system capable of expressing heterologous genes or gene fragments, whether intracellularly or extracellularly would be similarly acceptable.

[0044] For use particularly in detecting the presence and/or location of a human GluR3 receptor, for example in brain tissue, the present invention also provides, in another of its aspects, labelled antibody to a human GluR3 receptor. To raise such antibodies, there may be used as immunogen either the intact, soluble receptor or an immunogenic fragment thereof i.e. a fragment capable of eliciting an immune response, produced in a microbial or mammalian cell host as described above or by standard peptide synthesis techniques. Regions of human GluR3 receptor particularly suitable for use as immunogenic fragments include those corresponding in sequence to an extracellular region of the receptor, or a portion of the extracellular region, such as peptides consisting of residues 1-526 or a fragment thereof comprising at least about 10 residues, including particularly fragments containing residues 178-193 01479-522; and peptides corresponding to the region between transmembrane domains TM-2 and TM-3, such as a peptide consisting of residues 594-603. Peptides consisting of the C-terminal domain (residues 817-866), or fragment thereof, may also be used for the raising of antibodies.

[0045] The raising of antibodies to the selected human GluR3 receptor or immunogenic fragment can be achieved, for polyclonal antibody production, using immunization protocols of conventional design, and any of a variety of mammalian hosts, such as sheep, goats and rabbits. Alternatively, for monoclonal antibody production, immunocytes such as splenocytes can be recovered from the immunized animal and fused, using hybridoma technology, to a myeloma cells. The fusion products are then screened by culturing in a selection medium, and cells producing antibody are recovered for continuous growth, and antibody recovery. Recovered antibody can then be coupled covalently to a detectable label, such as a radiolabel, enzyme label, luminescent label or the like, using linker technology established for this purpose.

[0046] In detectably labelled form, e.g. radiolabelled form, DNA or RNA coding for a human GluR3 receptor, and selected regions thereof, may also be used, in accordance with another aspect of the present invention, as hybridization probes for example to identify sequence-related genes resident in the human or other mammalian genomes (or cDNA libraries) or to locate the human GluR3-encoding DNA in a specimen, such as brain tissue. This can be done using either the intact coding region, or a fragment thereof having radiolabelled e.g. ³²P, nucleotides incorporated therein. To identify the human GluR3-encoding DNA in a specimen, it is desirable to use either the full length cDNA coding therefor, or a fragment which is unique thereto. With reference to FIGS. 1A-1E and 3A-3F and SEQ ID NOs. 1-4, such nucleotide fragments include those comprising at least about 17 nucleic acids, and otherwise corresponding in sequence to a region coding for an extracellular N-terminal or C-terminal region of the receptor, or representing a 5′-untranslated or 3′-untranslated region thereof. Such oligonucleotide sequences, and the intact gene itself, may also be used of course to clone human GluR3-related human genes, particularly cDNA equivalents thereof, by standard hybridization techniques.

EXAMPLE 1 Isolation of DNA Coding for the Human GluR3A Receptor

[0047] The particular strategy used to clone the human GluR3A receptor is depicted schematically in FIG. 2, and described in greater detail below.

[0048] cDNA coding for the human GluR3A receptor was identified by probing human hippocampal cDNA that was obtained as an EcoRI-based lambda phage library (lambda ZAP) from Stratagene Cloning Systems (La Jolla, Calif., U.S.A.). The cDNA library was probed initially with a 1.1 kb EcoRI/EcoRI DNA fragment constituting the 3′ region of a kainate-binding human EAA receptor, designated humEAAla. This particular kainate-binding receptor is described in our co-pending U.S. patent application Ser. No. 07/750,090 filed Aug. 26, 1991 and incorporated herein by reference. DNA coding for the human EAA1 a receptor, and from which the 1.1 kb probe may be recovered, was deposited under terms of the Budapest Treaty, with the American Type Culture Collection in Rockville, Md. U.S.A. on Aug. 21, 1991 under accession number ATCC 75063.

[0049] Hybridizations using the probe were carried out at 30C overnight, and filters were washed with 2×SSC containing 0.5% SDS at 25C for 5 minutes, followed by a 15 minute wash at 50C with 2×SSC containing 0.5% SDS. The final wash was with 1×SSC containing 0.5% SDS at 50C for 15 minutes. Filters were exposed to X-ray film (Kodak) overnight. Of 106 clones screened under the following hybridization conditions (6×SSC, 50% formamide, 5% Denhardt's solution, 0.5% SDS, 100 ug/ml denatured salmon sperm DNA), only two hippocampal cDNA library inserts were identified, one about 1.6 kb and designated RKCH521 and another about 2.2 kb and designated RKCH221 (FIG. 2). For sequencing, the '521 and the '221 phages were plaque purified, then excised as phagemids according to the supplier's specifications, to generate insert-carrying Bluescript-SK variants of the phagemid vector. Sequencing of the '221 clone across its entire sequence revealed a putative ATG initiation codon together with about 78 bases of 5′non-coding region and about 2.1 kb of coding region. Sequencing across the '521 insert revealed a significant region of overlap with the '221 insert, and provided some additional 3′ sequence, although no termination codon was located.

[0050] There being no termination codon apparent in the '521 sequence, a 3′ region of the gene was sought. For this purpose, there was first synthesized an oligonucleotide probe capable of annealing to the 3′ region of the rat GluR3 receptor sequence (SEQ ID NO: 7) reported by Keinanen et al, supra. The specific sequence of the 32-P-labelled probe is provided below:

[0051] 5′-ACACTCAGAATTACGCTACATACAGAGAAGGCTACAACGT-3′

[0052] The same hippocampal cDNA library was then re-screened using the rat-based probe and under the following hybridization conditions; 6×SSC, 25% formamide, 5% Dernhardt's solution, 0.5% SDS, 100 ug/ml denatured salmon sperm DNA, 42C. This revealed a 1.2 kb insert, designated RKCSHG132. Sequencing of the entire insert revealed 5′ overlap with the 3′ end of the previously isolated '521 insert, and also revealed a termination codon as well as about 15 bases of 3′non-translated sequence.

[0053] To provide the entire coding region in an intact clone, the strategy shown in FIG. 2 was employed, to generate the phagemid pBS/humGluR3A which carries the hGluR3A-encoding DNA as a 2.8 kb EcoRI/EcoRI insert in a 3.0 kb Bluescript-SK phagemid background. The entire sequence of the EcoRI/EcoRI insert is provided in FIGS. 1A-1E and SEQ ID NO: 1.

[0054] The 5.8 kb phagemid pBS/humGluR3A was deposited, under the terms of the Budapest Treaty, with the American Type Culture Collection in Rockville, Md. USA on Mar. 19, 1992, and has been assigned accession number ATCC 75218.

EXAMPLE 2 Isolation of DNA Coding for Human GluR3B Receptor

[0055] A human fetal brain cDNA library was also screened in the search for human GluR receptors. This particular library was obtained as an EcoRI-based lambda gt10 library from Strategene Cloning Systems (La Jolla, Calif., U.S.A.). The library was first screened using as hybridization probe an oligonucleotide capable of hybridizing to a 3′ region of the reported rat GluR3 gene sequence. Screening using hybridization conditions as noted above (6×SSC, 25% formamide, 42C, etc.) revealed one insert about 2.3 kb in size, designated RKCSFG34. After excision to release Bluescript-SK phagemids carrying the insert, sequencing revealed substantial sequence identity between the '34 insert and the 3′ end of the earlier isolated GluR3A clone, and suggested that the 5′ end of the gene encoded on partially on the '34 insert was missing. To provide an assembled gene, a 5′ region was excised from the GluR3A insert and used to generate the 5′ end of the '34 insert, at an internal HindIII site. This was achieved as depicted schematically in FIG. 4. The resulting intact clone was designated human GluR3B.

[0056] Sequence comparison between the GluR3A clone of example 1 and the GluR3B clone of this example revealed only a short region of dissimilarity which is illustrated, in terms of amino acid sequence, in FIG. 6 (the sequences are also shown in SEQ ID NOs. 5 and 6).

[0057] The 6.1 kb phagemid pBS/humGluR3B was deposited, under the terms of the Budapest Treaty, with the American Type Culture Collection in Rockville, Md. USA on Mar. 19, 1992, and has been assigned accession number ATCC 75219.

EXAMPLE 3 Construction of Genetically Engineered Cells Producing Human GluR3 Receptor

[0058] For transient expression in mammalian cells, cDNA coding for the human GluR3A receptor was incorporated into the mammalian expression vector pcDNAI, which is available commercially from Invitrogen Corporation (San Diego, Calif., USA; catalogue number V490-20). This is a multifunctional 4.2 kb plasmid vector designed for cDNA expression in eukaryotic systems, and cDNA analysis in prokaryotes. Incorporated on the vector are the CMV promoter and enhancer, splice segment and polyadenylation signal, an SV40 and Polyoma virus origin of replication, and M13 origin to rescue single strand DNA for sequencing and mutagenesis, Sp6 and T7 RNA promoters for the production of sense and anti-sense RNA transcripts and a Col E1-like high copy plasmid origin. A polylinker is located appropriately downstream of the CMV promoter (and 3′ of the T7 promoter).

[0059] To facilitate incorporation of the GluR3A receptor-encoding cDNA into an expression vector, a NotI site was introduced onto the 5′ flank of the Bluescript-SK cDNA insert, and the cDNA insert was then released from pBS/humGluR3A as a 2.8 kb NotI/NotI fragment, which was then incorporated at the NotI site in the pcDNAI polylinker. Sequencing across the NotI junction was performed, to confirm proper insert orientation in pcDNAI. The resulting plasmid, designated pcDNAI/humGluR3A, was then introduced for transient expression into a selected mammalian cell host, in this case the monkey-derived, fibroblast like cells of the COS-1 lineage (available from the American Type Culture Collection, Rockville, Md. as ATCC CRL 1650).

[0060] For transient expression of the GluR3A-encoding DNA, COS-1 cells were transfected with approximately 8 ug DNA (as pcDNA1/humGluR3A) per 106 COS cells, by DEAE-mediated DNA transfection and treated with chloroquine according to the procedures described by Maniatis et al, supra. Briefly, COS-1 cells were plated at a density of 5×10⁶ cells/dish and then grown for 24 hours in FBS-supplemented DMEM/F12 medium. Medium was then removed and cells were washed in PBS and then in medium. There was then applied on the cells 10 ml of a transfection solution containing DEAE dextran (0.4 mg/ml), 100 μM chloroquine, 10% NuSerum, DNA (0.4 mg/ml) in DMEM/F12 medium. After incubation for 3 hours at 37C, cells were washed in PBS and medium as just described and then shocked for 1 minute with 10% DMSO in DMEM/F12 medium. Cells were allowed to grow for 2-3 days in 10% FBS-supplemented medium, and at the end of incubation dishes were placed on ice, washed with ice cold PBS and then removed by scraping. Cells were then harvested by centrifugation at 1000 rpm for 10 minutes and the cellular pellet was frozen in liquid nitrogen, for subsequent use in ligand binding assays. Northern blot analysis of a thawed aliquot of frozen cells confirmed expression of receptor-encoding cDNA in cells under storage.

[0061] In a like manner, stably transfected cell lines can also prepared using two different cell types as host: CHO K1 and CHO Pro5. To construct these cell lines, cDNA coding for human GluR3A was incorporated into the mammalian expression vector pRC/CMV (Invitrogen), which enables stable expression. Insertion at this site placed the cDNA under the expression control of the cytomegalovirus promoter and upstream of the polyadenylation site and terminator of the bovine growth hormone gene, and into a vector background comprising the neomycin resistance gene (driven by the SV40 early promoter) as selectable marker.

[0062] To introduce plasmids constructed as described above, the host CHO cells are first seeded at a density of 5×10⁵ in 10% FBS-supplemented MEM medium. After growth for 24 hours, fresh medium are added to the plates and three hours later, the cells are transfected using the calcium phosphate-DNA co-precipitation procedure (Maniatis et al, supra). Briefly, 3 ug of DNA is mixed and incubated with buffered calcium solution for 10 minutes at room temperature. An equal volume of buffered phosphate solution is added and the suspension is incubated for 15 minutes at room temperature. Next, the incubated suspension is applied to the cells for 4 hours, removed and cells were shocked with medium containing 15% glycerol. Three minutes later, cells are washed with medium and incubated for 24 hours at normal growth conditions. Cells resistant to neomycin are selected in 10% FBS-supplemented alpha-MEM medium containing G418 (1 mg/ml). Individual colonies of G418-resistant cells are isolated about 2-3 weeks later, clonally selected and then propogated for assay purposes.

EXAMPLE 4 Ligand Binding Assays

[0063] Transfected cells in the frozen state were resuspended in ice-cold distilled water using a hand homogenizer, sonicated for 5 seconds, and then centrifuged for 20 minutes at 50,000 g. The supernatant was discarded and the membrane pellet stored frozen at −70C.

[0064] COS cell membrane pellets were suspended in ice cold 50 mM Tris-HCl (pH 7.55, 5C) and centrifuged again at 50,000 g for 10 minutes in order to remove endogenous glutamate that would compete for binding. Pellets were resuspended in ice cold 50 mM Tris-HCl (pH 7.55) buffer and the resultant membrane preparation was used as tissue source for binding experiments described below. Proteins were determined using the Pierce Reagent with BSA as standard.

[0065] Binding assays were then performed, using an amount of COS-derived membrane equivalent to from 25-100 ug as judged by protein determination and selected radiolabelled ligand. In particular, for AMPA-binding assays, incubation mixtures consisted of 25-100 ug tissue protein and D,L-alpha-[5-methyl-3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid (3H-AMPA, 27.6Ci/mmole, 10 nM final) with 0.1M KSCN and 2.5 mM CaCl₂ in the 1 ml final volume. Non-specific binding was determined in the presence of 1 mM L-glutamate. Samples were incubated on ice for 60 minutes in plastic minivials, and bound and free ligand were separated by centrifugation for 30 minutes at 50,000 g. Pellets were washed twice in 6 ml of the cold incubation buffer, then 5 ml of Beckman Ready-Protein Plus scintillation cocktail was added, for counting.

[0066] For kainate-binding assays, incubation mixtures consisted of 25-100 ug tissue protein and [vinylidene-3H] kainic acid (58Ci/mmole, 5 nM final) in the cold incubation buffer, 1 ml final volume. Non-specific binding was determined in the presence of 1 mM L-glutamate. Samples were incubated as for the AMPA-binding assays, and bound and free ligand were separated by rapid filtration using a Brandel cell harvester and GF/B filters pre-soaked in ice-cold 0.3% polyethyleneimine. Filters were washed twice in 6 ml of the cold incubation buffer, then placed in scintillation vials with 5 ml of Beckman Ready-Protein Plus scintillation cocktail for counting.

[0067] Assays performed in this manner, using membrane preparations derived from the human GluR3A receptor-producing COS cells, revealed specific binding of 25-30 fmole/mg protein, at 10 nM [3H]-AMPA (FIG. 7). Mock transfected cells exhibited no specific binding of any of the ligands tested. These results demonstrate clearly that the human GluR3 receptor is binding AMPA with specificity. This activity, coupled with the fact that there is little or no demonstrable binding of either kainate or NMDA, clearly assigns the human GluR3 receptor to be of the AMPA type of EAA receptor. Furthermore, this binding profile indicates that the receptor is binding in an authentic manner, and can therefore reliably predict the ligand binding “signature” of its non-recombinant counterpart from the human brain. These features make the recombinant receptor especially useful for selecting and characterizing ligand compounds which bind to the receptor, and/or for selecting and characterizing compounds which may act by displacing other ligands from the receptor. The isolation of the GluR3 receptor genes in substantially pure form, capable of being expressed as a single, homogeneous receptor species, therefore frees the ligand binding assay from the lack of precision introduced when complex, heterogeneous receptor preparations from human and other mammalian brains are used to attempt such characterizations.

1 7 2761 base pairs nucleic acid double linear cDNA sig_peptide 79..144 mat_peptide 145..2745 CDS 79..2745 1 GAATTCCTGA CGACTCCTGA GTTGCGCCCA TGCTCTTGTC AGCTTCGTTT TAGGCGTAGC 60 ATGGCCAGGC AGAAGAAA ATG GGG CAA AGC GTG CTC CGG GCG GTC TTC TTT 111 Met Gly Gln Ser Val Leu Arg Ala Val Phe Phe -22 -20 -15 TTA GTC CTG GGG CTT TTG GGT CAT TCT CAC GGA GGA TTC CCC AAC ACC 159 Leu Val Leu Gly Leu Leu Gly His Ser His Gly Gly Phe Pro Asn Thr -10 -5 1 5 ATC AGC ATA GGT GGA CTT TTC ATG AGA AAC ACA GTG CAG GAG CAC AGC 207 Ile Ser Ile Gly Gly Leu Phe Met Arg Asn Thr Val Gln Glu His Ser 10 15 20 GCT TTC CGC TTT GCC GTG CAG TTA TAC AAC ACC AAC CAG AAC ACC ACC 255 Ala Phe Arg Phe Ala Val Gln Leu Tyr Asn Thr Asn Gln Asn Thr Thr 25 30 35 GAG AAG CCC TTC CAT TTG AAT TAC CAC GTA GAT CAC TTG GAT TCC TCC 303 Glu Lys Pro Phe His Leu Asn Tyr His Val Asp His Leu Asp Ser Ser 40 45 50 AAT AGT TTT TCC GTG ACA AAT GCT TTC TGC TCC CAG TTC TCG AGA GGG 351 Asn Ser Phe Ser Val Thr Asn Ala Phe Cys Ser Gln Phe Ser Arg Gly 55 60 65 GTG TAT GCC ATC TTT GGA TTC TAT GAC CAG ATG TCA ATG AAC ACC CTG 399 Val Tyr Ala Ile Phe Gly Phe Tyr Asp Gln Met Ser Met Asn Thr Leu 70 75 80 85 ACC TCC TTC TGT GGG GCC CTG CAC ACA TCC TTT GTT ACG CCT AGC TTC 447 Thr Ser Phe Cys Gly Ala Leu His Thr Ser Phe Val Thr Pro Ser Phe 90 95 100 CCC ACT GAC GCA GAT GTG CAG TTT GTC ATC CAG ATG CGC CCA GCC TTG 495 Pro Thr Asp Ala Asp Val Gln Phe Val Ile Gln Met Arg Pro Ala Leu 105 110 115 AAG GGC GCT ATT CTG AGT CTT CTG GGT CAT TAC AAG TGG GAG AAG TTT 543 Lys Gly Ala Ile Leu Ser Leu Leu Gly His Tyr Lys Trp Glu Lys Phe 120 125 130 GTG TAC CTC TAT GAC ACA GAA CGA GGA TTT TCC ATC CTC CAA GCG ATT 591 Val Tyr Leu Tyr Asp Thr Glu Arg Gly Phe Ser Ile Leu Gln Ala Ile 135 140 145 ATG GAA GCA GCA GTG CAA AAC AAC TGG CAA GTA ACA GCA AGG TCT GTG 639 Met Glu Ala Ala Val Gln Asn Asn Trp Gln Val Thr Ala Arg Ser Val 150 155 160 165 GGA AAC ATA AAG GAC GTC CAA GAA TTC AGG CGC ATC ATT GAA GAA ATG 687 Gly Asn Ile Lys Asp Val Gln Glu Phe Arg Arg Ile Ile Glu Glu Met 170 175 180 GAC AGG AGG CAG GAA AAG CGA TAC TTG ATT GAC TGC GAA GTC GAA AGG 735 Asp Arg Arg Gln Glu Lys Arg Tyr Leu Ile Asp Cys Glu Val Glu Arg 185 190 195 ATT AAC ACA ATT TTG GAA CAG GTT GTG ATC CTA GGG AAA CAC TCA AGA 783 Ile Asn Thr Ile Leu Glu Gln Val Val Ile Leu Gly Lys His Ser Arg 200 205 210 GGT TAT CAC TAC ATG CTC GCT AAC CTG GGT TTT ACT GAT ATT TTA CTG 831 Gly Tyr His Tyr Met Leu Ala Asn Leu Gly Phe Thr Asp Ile Leu Leu 215 220 225 GAA AGA GTC ATG CAT GGG GGA GCC AAC ATT ACA GGT TTC CAG ATT GTC 879 Glu Arg Val Met His Gly Gly Ala Asn Ile Thr Gly Phe Gln Ile Val 230 235 240 245 AAC AAT GAA AAC CCT ATG GTT CAG CAG TTC ATA CAG CGC TGG GTG AGG 927 Asn Asn Glu Asn Pro Met Val Gln Gln Phe Ile Gln Arg Trp Val Arg 250 255 260 CTG GAT GAA AGG GAA TTC CCT GAA GCC AAG AAT GCA CCA CTA AAG TAT 975 Leu Asp Glu Arg Glu Phe Pro Glu Ala Lys Asn Ala Pro Leu Lys Tyr 265 270 275 ACA TCT GCA TTG ACA CAC GAC GCA ATA CTG GTC ATA GCA GAA GCT TTC 1023 Thr Ser Ala Leu Thr His Asp Ala Ile Leu Val Ile Ala Glu Ala Phe 280 285 290 CGC TAC CTG AGG AGG CAG CGA GTA GAT GTG TCC CGG AGA GGA AGT GCT 1071 Arg Tyr Leu Arg Arg Gln Arg Val Asp Val Ser Arg Arg Gly Ser Ala 295 300 305 GGA GAC TGC TTA GCA AAT CCT GCT GTG CCC TGG AGT CAA GGA ATT GAT 1119 Gly Asp Cys Leu Ala Asn Pro Ala Val Pro Trp Ser Gln Gly Ile Asp 310 315 320 325 ATT GAG AGA GCT CTG AAA ATG GTG CAA GTA CAA GGA ATG ACT GGA AAT 1167 Ile Glu Arg Ala Leu Lys Met Val Gln Val Gln Gly Met Thr Gly Asn 330 335 340 ATT CAA TTT GAC ACT TAT GGA CGT AGG ACA AAT TAT ACC ATC GAT GTG 1215 Ile Gln Phe Asp Thr Tyr Gly Arg Arg Thr Asn Tyr Thr Ile Asp Val 345 350 355 TAT GAA ATG AAA GTC AGT GGC TCT CGA AAA GCT GGC TAC TGG AAC GAG 1263 Tyr Glu Met Lys Val Ser Gly Ser Arg Lys Ala Gly Tyr Trp Asn Glu 360 365 370 TAT GAA AGG TTT GTG CCT TTC TCA GAT CAG CAA ATC AGC AAT GAC AGT 1311 Tyr Glu Arg Phe Val Pro Phe Ser Asp Gln Gln Ile Ser Asn Asp Ser 375 380 385 GCA TCC TCA GAG AAT CGG ACC ATA GTA GTG ACT ACC ATT CTG GAA TCA 1359 Ala Ser Ser Glu Asn Arg Thr Ile Val Val Thr Thr Ile Leu Glu Ser 390 395 400 405 CCA TAT GTA ATG TAC AAG AAG AAC CAT GAG CAA CTG GAA GGA AAT GAA 1407 Pro Tyr Val Met Tyr Lys Lys Asn His Glu Gln Leu Glu Gly Asn Glu 410 415 420 CGA TAT GAA GGC TAT TGT GTA GAC CTA GCC TAT GAA ATA GCC AAA CAT 1455 Arg Tyr Glu Gly Tyr Cys Val Asp Leu Ala Tyr Glu Ile Ala Lys His 425 430 435 GTA AGG ATC AAA TAC AAA TTG TCC ATC GTT GGT GAC GGG AAA TAT GGT 1503 Val Arg Ile Lys Tyr Lys Leu Ser Ile Val Gly Asp Gly Lys Tyr Gly 440 445 450 GCA AGG GAT CCA GAG ACT AAA ATA TGG AAC GGC ATG GTT GGG GAA CTT 1551 Ala Arg Asp Pro Glu Thr Lys Ile Trp Asn Gly Met Val Gly Glu Leu 455 460 465 GTC TAT GGG AGA GCT GAT ATA GCT GTT GCT CCA CTC ACT ATA ACA TTG 1599 Val Tyr Gly Arg Ala Asp Ile Ala Val Ala Pro Leu Thr Ile Thr Leu 470 475 480 485 GTC CGT GAA GAA GTC ATA GAT TTT TCA AAG CCA TTA ATG AGC CTG GGC 1647 Val Arg Glu Glu Val Ile Asp Phe Ser Lys Pro Leu Met Ser Leu Gly 490 495 500 ATC TCC ATC ATG ATA AAG AAG CCT CAG AAA TCA AAA CCA GGC GTA TTC 1695 Ile Ser Ile Met Ile Lys Lys Pro Gln Lys Ser Lys Pro Gly Val Phe 505 510 515 TCA TTT CTG GAT CCC CTG GCT TAT GAA ATC TGG ATG TGC ATT GTC TTT 1743 Ser Phe Leu Asp Pro Leu Ala Tyr Glu Ile Trp Met Cys Ile Val Phe 520 525 530 GCT TAC ATT GGA GTC AGC GTA GTT CTT TTC CTA GTC AGC AGG TTC AGT 1791 Ala Tyr Ile Gly Val Ser Val Val Leu Phe Leu Val Ser Arg Phe Ser 535 540 545 CCT TAT GAA TGG CAC TTG GAA GAC AAC AAT GAA GAA CCT CGT GAC CCA 1839 Pro Tyr Glu Trp His Leu Glu Asp Asn Asn Glu Glu Pro Arg Asp Pro 550 555 560 565 CAA AGT CCT CCT GAT CCT CCA AAT GAA TTT GGA ATA TTT AAC AGT CTT 1887 Gln Ser Pro Pro Asp Pro Pro Asn Glu Phe Gly Ile Phe Asn Ser Leu 570 575 580 TGG TTT TCC TTG GGT GCC TTT ATG CAG CAA GGA TGT GAT ATT TCT CCA 1935 Trp Phe Ser Leu Gly Ala Phe Met Gln Gln Gly Cys Asp Ile Ser Pro 585 590 595 AGA TCA CTC TCC GGG CGC ATT GTT GGA GGG GTT TGG TGG TTC TTC ACC 1983 Arg Ser Leu Ser Gly Arg Ile Val Gly Gly Val Trp Trp Phe Phe Thr 600 605 610 CTG ATC ATA ATT TCT TCC TAT ACT GCC AAT CTC GCT GCT TTC CTG ACT 2031 Leu Ile Ile Ile Ser Ser Tyr Thr Ala Asn Leu Ala Ala Phe Leu Thr 615 620 625 GTG GAG AGG ATG GTT TCT CCC ATA GAG AGT GCT GAA GAC TTA GCT AAA 2079 Val Glu Arg Met Val Ser Pro Ile Glu Ser Ala Glu Asp Leu Ala Lys 630 635 640 645 CAG ACT GAA ATT GCA TAT GGG ACC CTG GAC TCC GGT TCA ACA AAA GAA 2127 Gln Thr Glu Ile Ala Tyr Gly Thr Leu Asp Ser Gly Ser Thr Lys Glu 650 655 660 TTT TTC AGA AGA TCC AAA ATT GCT GTG TAC GAG AAA ATG TGG TCT TAC 2175 Phe Phe Arg Arg Ser Lys Ile Ala Val Tyr Glu Lys Met Trp Ser Tyr 665 670 675 ATG AAA TCA GCG GAG CCA TCT GTG TTT ACC AAA ACA ACA GCA GAC GGA 2223 Met Lys Ser Ala Glu Pro Ser Val Phe Thr Lys Thr Thr Ala Asp Gly 680 685 690 GTG GCC CGA GTG CGA AAG TCC AAG GGA AAG TTC GCC TTC CTG CTG GAG 2271 Val Ala Arg Val Arg Lys Ser Lys Gly Lys Phe Ala Phe Leu Leu Glu 695 700 705 TCA ACC ATG AAT GAG TAC ATT GAG CAG AGA AAA CCA TGT GAT ACG ATG 2319 Ser Thr Met Asn Glu Tyr Ile Glu Gln Arg Lys Pro Cys Asp Thr Met 710 715 720 725 AAA GTT GGT GGA AAT CTG GAT TCC AAA GGC TAT GGT GTG GCA ACC CCT 2367 Lys Val Gly Gly Asn Leu Asp Ser Lys Gly Tyr Gly Val Ala Thr Pro 730 735 740 AAA GGC TCA GCA TTA GGA AAT GCT GTT AAC CTG GCA GTA TTA AAA CTG 2415 Lys Gly Ser Ala Leu Gly Asn Ala Val Asn Leu Ala Val Leu Lys Leu 745 750 755 AAT GAG CAA GGC CTC TTG GAC AAA TTG AAA AAC AAA TGG TGG TAC GAC 2463 Asn Glu Gln Gly Leu Leu Asp Lys Leu Lys Asn Lys Trp Trp Tyr Asp 760 765 770 AAA GGA GAG TGC GGC AGC GGG GGC GGT GAC TCC AAG GAC AAG ACC AGC 2511 Lys Gly Glu Cys Gly Ser Gly Gly Gly Asp Ser Lys Asp Lys Thr Ser 775 780 785 GCT CTG AGC CTG AGC AAT GTG GCA GGC GTT TTC TAT ATA CTT GTC GGA 2559 Ala Leu Ser Leu Ser Asn Val Ala Gly Val Phe Tyr Ile Leu Val Gly 790 795 800 805 GGT CTG GGG CTG GCC ATG ATG GTG GCT TTG ATA GAA TTC TGT TAC AAA 2607 Gly Leu Gly Leu Ala Met Met Val Ala Leu Ile Glu Phe Cys Tyr Lys 810 815 820 TCA CGG GCA GAG TCC AAA CGC ATG AAA CTC ACA AAG AAC ACC CAA AAC 2655 Ser Arg Ala Glu Ser Lys Arg Met Lys Leu Thr Lys Asn Thr Gln Asn 825 830 835 TTT AAG CCT GCT CCT GCC ACC AAC ACT CAG AAT TAT GCT ACA TAC AGA 2703 Phe Lys Pro Ala Pro Ala Thr Asn Thr Gln Asn Tyr Ala Thr Tyr Arg 840 845 850 GAA GGC TAC AAC GTG TAT GGA ACA GAG AGT GTT AAG ATC TAGGGATCCC 2752 Glu Gly Tyr Asn Val Tyr Gly Thr Glu Ser Val Lys Ile 855 860 865 TTGGAATTC 2761 888 amino acids amino acid linear protein 2 Met Gly Gln Ser Val Leu Arg Ala Val Phe Phe Leu Val Leu Gly Leu -22 -20 -15 -10 Leu Gly His Ser His Gly Gly Phe Pro Asn Thr Ile Ser Ile Gly Gly -5 1 5 10 Leu Phe Met Arg Asn Thr Val Gln Glu His Ser Ala Phe Arg Phe Ala 15 20 25 Val Gln Leu Tyr Asn Thr Asn Gln Asn Thr Thr Glu Lys Pro Phe His 30 35 40 Leu Asn Tyr His Val Asp His Leu Asp Ser Ser Asn Ser Phe Ser Val 45 50 55 Thr Asn Ala Phe Cys Ser Gln Phe Ser Arg Gly Val Tyr Ala Ile Phe 60 65 70 Gly Phe Tyr Asp Gln Met Ser Met Asn Thr Leu Thr Ser Phe Cys Gly 75 80 85 90 Ala Leu His Thr Ser Phe Val Thr Pro Ser Phe Pro Thr Asp Ala Asp 95 100 105 Val Gln Phe Val Ile Gln Met Arg Pro Ala Leu Lys Gly Ala Ile Leu 110 115 120 Ser Leu Leu Gly His Tyr Lys Trp Glu Lys Phe Val Tyr Leu Tyr Asp 125 130 135 Thr Glu Arg Gly Phe Ser Ile Leu Gln Ala Ile Met Glu Ala Ala Val 140 145 150 Gln Asn Asn Trp Gln Val Thr Ala Arg Ser Val Gly Asn Ile Lys Asp 155 160 165 170 Val Gln Glu Phe Arg Arg Ile Ile Glu Glu Met Asp Arg Arg Gln Glu 175 180 185 Lys Arg Tyr Leu Ile Asp Cys Glu Val Glu Arg Ile Asn Thr Ile Leu 190 195 200 Glu Gln Val Val Ile Leu Gly Lys His Ser Arg Gly Tyr His Tyr Met 205 210 215 Leu Ala Asn Leu Gly Phe Thr Asp Ile Leu Leu Glu Arg Val Met His 220 225 230 Gly Gly Ala Asn Ile Thr Gly Phe Gln Ile Val Asn Asn Glu Asn Pro 235 240 245 250 Met Val Gln Gln Phe Ile Gln Arg Trp Val Arg Leu Asp Glu Arg Glu 255 260 265 Phe Pro Glu Ala Lys Asn Ala Pro Leu Lys Tyr Thr Ser Ala Leu Thr 270 275 280 His Asp Ala Ile Leu Val Ile Ala Glu Ala Phe Arg Tyr Leu Arg Arg 285 290 295 Gln Arg Val Asp Val Ser Arg Arg Gly Ser Ala Gly Asp Cys Leu Ala 300 305 310 Asn Pro Ala Val Pro Trp Ser Gln Gly Ile Asp Ile Glu Arg Ala Leu 315 320 325 330 Lys Met Val Gln Val Gln Gly Met Thr Gly Asn Ile Gln Phe Asp Thr 335 340 345 Tyr Gly Arg Arg Thr Asn Tyr Thr Ile Asp Val Tyr Glu Met Lys Val 350 355 360 Ser Gly Ser Arg Lys Ala Gly Tyr Trp Asn Glu Tyr Glu Arg Phe Val 365 370 375 Pro Phe Ser Asp Gln Gln Ile Ser Asn Asp Ser Ala Ser Ser Glu Asn 380 385 390 Arg Thr Ile Val Val Thr Thr Ile Leu Glu Ser Pro Tyr Val Met Tyr 395 400 405 410 Lys Lys Asn His Glu Gln Leu Glu Gly Asn Glu Arg Tyr Glu Gly Tyr 415 420 425 Cys Val Asp Leu Ala Tyr Glu Ile Ala Lys His Val Arg Ile Lys Tyr 430 435 440 Lys Leu Ser Ile Val Gly Asp Gly Lys Tyr Gly Ala Arg Asp Pro Glu 445 450 455 Thr Lys Ile Trp Asn Gly Met Val Gly Glu Leu Val Tyr Gly Arg Ala 460 465 470 Asp Ile Ala Val Ala Pro Leu Thr Ile Thr Leu Val Arg Glu Glu Val 475 480 485 490 Ile Asp Phe Ser Lys Pro Leu Met Ser Leu Gly Ile Ser Ile Met Ile 495 500 505 Lys Lys Pro Gln Lys Ser Lys Pro Gly Val Phe Ser Phe Leu Asp Pro 510 515 520 Leu Ala Tyr Glu Ile Trp Met Cys Ile Val Phe Ala Tyr Ile Gly Val 525 530 535 Ser Val Val Leu Phe Leu Val Ser Arg Phe Ser Pro Tyr Glu Trp His 540 545 550 Leu Glu Asp Asn Asn Glu Glu Pro Arg Asp Pro Gln Ser Pro Pro Asp 555 560 565 570 Pro Pro Asn Glu Phe Gly Ile Phe Asn Ser Leu Trp Phe Ser Leu Gly 575 580 585 Ala Phe Met Gln Gln Gly Cys Asp Ile Ser Pro Arg Ser Leu Ser Gly 590 595 600 Arg Ile Val Gly Gly Val Trp Trp Phe Phe Thr Leu Ile Ile Ile Ser 605 610 615 Ser Tyr Thr Ala Asn Leu Ala Ala Phe Leu Thr Val Glu Arg Met Val 620 625 630 Ser Pro Ile Glu Ser Ala Glu Asp Leu Ala Lys Gln Thr Glu Ile Ala 635 640 645 650 Tyr Gly Thr Leu Asp Ser Gly Ser Thr Lys Glu Phe Phe Arg Arg Ser 655 660 665 Lys Ile Ala Val Tyr Glu Lys Met Trp Ser Tyr Met Lys Ser Ala Glu 670 675 680 Pro Ser Val Phe Thr Lys Thr Thr Ala Asp Gly Val Ala Arg Val Arg 685 690 695 Lys Ser Lys Gly Lys Phe Ala Phe Leu Leu Glu Ser Thr Met Asn Glu 700 705 710 Tyr Ile Glu Gln Arg Lys Pro Cys Asp Thr Met Lys Val Gly Gly Asn 715 720 725 730 Leu Asp Ser Lys Gly Tyr Gly Val Ala Thr Pro Lys Gly Ser Ala Leu 735 740 745 Gly Asn Ala Val Asn Leu Ala Val Leu Lys Leu Asn Glu Gln Gly Leu 750 755 760 Leu Asp Lys Leu Lys Asn Lys Trp Trp Tyr Asp Lys Gly Glu Cys Gly 765 770 775 Ser Gly Gly Gly Asp Ser Lys Asp Lys Thr Ser Ala Leu Ser Leu Ser 780 785 790 Asn Val Ala Gly Val Phe Tyr Ile Leu Val Gly Gly Leu Gly Leu Ala 795 800 805 810 Met Met Val Ala Leu Ile Glu Phe Cys Tyr Lys Ser Arg Ala Glu Ser 815 820 825 Lys Arg Met Lys Leu Thr Lys Asn Thr Gln Asn Phe Lys Pro Ala Pro 830 835 840 Ala Thr Asn Thr Gln Asn Tyr Ala Thr Tyr Arg Glu Gly Tyr Asn Val 845 850 855 Tyr Gly Thr Glu Ser Val Lys Ile 860 865 3070 base pairs nucleic acid double linear cDNA sig_peptide 79..144 mat_peptide 145..2745 CDS 79..2745 3 GAATTCCTGA CGACTCCTGA GTTGCGCCCA TGCTCTTGTC AGCTTCGTTT TAGGCGTAGC 60 ATGGCCAGGC AGAAGAAA ATG GGG CAA AGC GTG CTC CGG GCG GTC TTC TTT 111 Met Gly Gln Ser Val Leu Arg Ala Val Phe Phe -22 -20 -15 TTA GTC CTG GGG CTT TTG GGT CAT TCT CAC GGA GGA TTC CCC AAC ACC 159 Leu Val Leu Gly Leu Leu Gly His Ser His Gly Gly Phe Pro Asn Thr -10 -5 1 5 ATC AGC ATA GGT GGA CTT TTC ATG AGA AAC ACA GTG CAG GAG CAC AGC 207 Ile Ser Ile Gly Gly Leu Phe Met Arg Asn Thr Val Gln Glu His Ser 10 15 20 GCT TTC CGC TTT GCC GTG CAG TTA TAC AAC ACC AAC CAG AAC ACC ACC 255 Ala Phe Arg Phe Ala Val Gln Leu Tyr Asn Thr Asn Gln Asn Thr Thr 25 30 35 GAG AAG CCC TTC CAT TTG AAT TAC CAC GTA GAT CAC TTG GAT TCC TCC 303 Glu Lys Pro Phe His Leu Asn Tyr His Val Asp His Leu Asp Ser Ser 40 45 50 AAT AGT TTT TCC GTG ACA AAT GCT TTC TGC TCC CAG TTC TCG AGA GGG 351 Asn Ser Phe Ser Val Thr Asn Ala Phe Cys Ser Gln Phe Ser Arg Gly 55 60 65 GTG TAT GCC ATC TTT GGA TTC TAT GAC CAG ATG TCA ATG AAC ACC CTG 399 Val Tyr Ala Ile Phe Gly Phe Tyr Asp Gln Met Ser Met Asn Thr Leu 70 75 80 85 ACC TCC TTC TGT GGG GCC CTG CAC ACA TCC TTT GTT ACG CCT AGC TTC 447 Thr Ser Phe Cys Gly Ala Leu His Thr Ser Phe Val Thr Pro Ser Phe 90 95 100 CCC ACT GAC GCA GAT GTG CAG TTT GTC ATC CAG ATG CGC CCA GCC TTG 495 Pro Thr Asp Ala Asp Val Gln Phe Val Ile Gln Met Arg Pro Ala Leu 105 110 115 AAG GGC GCT ATT CTG AGT CTT CTG GGT CAT TAC AAG TGG GAG AAG TTT 543 Lys Gly Ala Ile Leu Ser Leu Leu Gly His Tyr Lys Trp Glu Lys Phe 120 125 130 GTG TAC CTC TAT GAC ACA GAA CGA GGA TTT TCC ATC CTC CAA GCG ATT 591 Val Tyr Leu Tyr Asp Thr Glu Arg Gly Phe Ser Ile Leu Gln Ala Ile 135 140 145 ATG GAA GCA GCA GTG CAA AAC AAC TGG CAA GTA ACA GCA AGG TCT GTG 639 Met Glu Ala Ala Val Gln Asn Asn Trp Gln Val Thr Ala Arg Ser Val 150 155 160 165 GGA AAC ATA AAG GAC GTC CAA GAA TTC AGG CGC ATC ATT GAA GAA ATG 687 Gly Asn Ile Lys Asp Val Gln Glu Phe Arg Arg Ile Ile Glu Glu Met 170 175 180 GAC AGG AGG CAG GAA AAG CGA TAC TTG ATT GAC TGC GAA GTC GAA AGG 735 Asp Arg Arg Gln Glu Lys Arg Tyr Leu Ile Asp Cys Glu Val Glu Arg 185 190 195 ATT AAC ACA ATT TTG GAA CAG GTT GTG ATC CTA GGG AAA CAC TCA AGA 783 Ile Asn Thr Ile Leu Glu Gln Val Val Ile Leu Gly Lys His Ser Arg 200 205 210 GGT TAT CAC TAC ATG CTC GCT AAC CTG GGT TTT ACT GAT ATT TTA CTG 831 Gly Tyr His Tyr Met Leu Ala Asn Leu Gly Phe Thr Asp Ile Leu Leu 215 220 225 GAA AGA GTC ATG CAT GGG GGA GCC AAC ATT ACA GGT TTC CAG ATT GTC 879 Glu Arg Val Met His Gly Gly Ala Asn Ile Thr Gly Phe Gln Ile Val 230 235 240 245 AAC AAT GAA AAC CCT ATG GTT CAG CAG TTC ATA CAG CGC TGG GTG AGG 927 Asn Asn Glu Asn Pro Met Val Gln Gln Phe Ile Gln Arg Trp Val Arg 250 255 260 CTG GAT GAA AGG GAA TTC CCT GAA GCC AAG AAT GCA CCA CTA AAG TAT 975 Leu Asp Glu Arg Glu Phe Pro Glu Ala Lys Asn Ala Pro Leu Lys Tyr 265 270 275 ACA TCT GCA TTG ACA CAC GAC GCA ATA CTG GTC ATA GCA GAA GCT TTC 1023 Thr Ser Ala Leu Thr His Asp Ala Ile Leu Val Ile Ala Glu Ala Phe 280 285 290 CGC TAC CTG AGG AGG CAG CGA GTA GAT GTG TCC CGG AGA GGA AGT GCT 1071 Arg Tyr Leu Arg Arg Gln Arg Val Asp Val Ser Arg Arg Gly Ser Ala 295 300 305 GGA GAC TGC TTA GCA AAT CCT GCT GTG CCC TGG AGT CAA GGA ATT GAT 1119 Gly Asp Cys Leu Ala Asn Pro Ala Val Pro Trp Ser Gln Gly Ile Asp 310 315 320 325 ATT GAG AGA GCT CTG AAA ATG GTG CAA GTA CAA GGA ATG ACT GGA AAT 1167 Ile Glu Arg Ala Leu Lys Met Val Gln Val Gln Gly Met Thr Gly Asn 330 335 340 ATT CAA TTT GAC ACT TAT GGA CGT AGG ACA AAT TAT ACC ATC GAT GTG 1215 Ile Gln Phe Asp Thr Tyr Gly Arg Arg Thr Asn Tyr Thr Ile Asp Val 345 350 355 TAT GAA ATG AAA GTC AGT GGC TCT CGA AAA GCT GGC TAC TGG AAC GAG 1263 Tyr Glu Met Lys Val Ser Gly Ser Arg Lys Ala Gly Tyr Trp Asn Glu 360 365 370 TAT GAA AGG TTT GTG CCT TTC TCA GAT CAG CAA ATC AGC AAT GAC AGT 1311 Tyr Glu Arg Phe Val Pro Phe Ser Asp Gln Gln Ile Ser Asn Asp Ser 375 380 385 GCA TCC TCA GAG AAT CGG ACC ATA GTA GTG ACT ACC ATT CTG GAA TCA 1359 Ala Ser Ser Glu Asn Arg Thr Ile Val Val Thr Thr Ile Leu Glu Ser 390 395 400 405 CCA TAT GTA ATG TAC AAG AAG AAC CAT GAG CAA CTG GAA GGA AAT GAA 1407 Pro Tyr Val Met Tyr Lys Lys Asn His Glu Gln Leu Glu Gly Asn Glu 410 415 420 CGA TAT GAA GGC TAT TGT GTA GAC CTA GCC TAT GAA ATA GCC AAA CAT 1455 Arg Tyr Glu Gly Tyr Cys Val Asp Leu Ala Tyr Glu Ile Ala Lys His 425 430 435 GTA AGG ATC AAA TAC AAA TTG TCC ATC GTT GGT GAC GGG AAA TAT GGT 1503 Val Arg Ile Lys Tyr Lys Leu Ser Ile Val Gly Asp Gly Lys Tyr Gly 440 445 450 GCA AGG GAT CCA GAG ACT AAA ATA TGG AAC GGC ATG GTT GGG GAA CTT 1551 Ala Arg Asp Pro Glu Thr Lys Ile Trp Asn Gly Met Val Gly Glu Leu 455 460 465 GTC TAT GGG AGA GCT GAT ATA GCT GTT GCT CCA CTC ACT ATA ACA TTG 1599 Val Tyr Gly Arg Ala Asp Ile Ala Val Ala Pro Leu Thr Ile Thr Leu 470 475 480 485 GTC CGT GAA GAA GTC ATA GAT TTT TCA AAG CCA TTA ATG AGC CTG GGC 1647 Val Arg Glu Glu Val Ile Asp Phe Ser Lys Pro Leu Met Ser Leu Gly 490 495 500 ATC TCC ATC ATG ATA AAG AAG CCT CAG AAA TCA AAA CCA GGC GTA TTC 1695 Ile Ser Ile Met Ile Lys Lys Pro Gln Lys Ser Lys Pro Gly Val Phe 505 510 515 TCA TTT CTG GAT CCC CTG GCT TAT GAA ATC TGG ATG TGC ATT GTC TTT 1743 Ser Phe Leu Asp Pro Leu Ala Tyr Glu Ile Trp Met Cys Ile Val Phe 520 525 530 GCT TAC ATT GGA GTC AGC GTA GTT CTT TTC CTA GTC AGC AGG TTC AGT 1791 Ala Tyr Ile Gly Val Ser Val Val Leu Phe Leu Val Ser Arg Phe Ser 535 540 545 CCT TAT GAA TGG CAC TTG GAA GAC AAC AAT GAA GAA CCT CGT GAC CCA 1839 Pro Tyr Glu Trp His Leu Glu Asp Asn Asn Glu Glu Pro Arg Asp Pro 550 555 560 565 CAA AGT CCT CCT GAT CCT CCA AAT GAA TTT GGA ATA TTT AAC AGT CTT 1887 Gln Ser Pro Pro Asp Pro Pro Asn Glu Phe Gly Ile Phe Asn Ser Leu 570 575 580 TGG TTT TCC TTG GGT GCC TTT ATG CAG CAA GGA TGT GAT ATT TCT CCA 1935 Trp Phe Ser Leu Gly Ala Phe Met Gln Gln Gly Cys Asp Ile Ser Pro 585 590 595 AGA TCA CTC TCC GGG CGC ATT GTT GGA GGG GTT TGG TGG TTC TTC ACC 1983 Arg Ser Leu Ser Gly Arg Ile Val Gly Gly Val Trp Trp Phe Phe Thr 600 605 610 CTG ATC ATA ATT TCT TCC TAT ACT GCC AAT CTC GCT GCT TTC CTG ACT 2031 Leu Ile Ile Ile Ser Ser Tyr Thr Ala Asn Leu Ala Ala Phe Leu Thr 615 620 625 GTG GAG AGG ATG GTT TCT CCC ATA GAG AGT GCT GAA GAC TTA GCT AAA 2079 Val Glu Arg Met Val Ser Pro Ile Glu Ser Ala Glu Asp Leu Ala Lys 630 635 640 645 CAG ACT GAA ATT GCA TAT GGG ACC CTG GAC TCC GGT TCA ACA AAA GAA 2127 Gln Thr Glu Ile Ala Tyr Gly Thr Leu Asp Ser Gly Ser Thr Lys Glu 650 655 660 TTT TTC AGA AGA TCC AAA ATT GCT GTG TAC GAG AAA ATG TGG TCT TAC 2175 Phe Phe Arg Arg Ser Lys Ile Ala Val Tyr Glu Lys Met Trp Ser Tyr 665 670 675 ATG AAA TCA GCG GAG CCA TCT GTG TTT ACC AAA ACA ACA GCA GAC GGA 2223 Met Lys Ser Ala Glu Pro Ser Val Phe Thr Lys Thr Thr Ala Asp Gly 680 685 690 GTG GCC CGA GTG CGA AAG TCC AAG GGA AAG TTC GCC TTC CTG CTG GAG 2271 Val Ala Arg Val Arg Lys Ser Lys Gly Lys Phe Ala Phe Leu Leu Glu 695 700 705 TCA ACC ATG AAT GAG TAC ATT GAG CAG AGA AAA CCA TGT GAT ACG ATG 2319 Ser Thr Met Asn Glu Tyr Ile Glu Gln Arg Lys Pro Cys Asp Thr Met 710 715 720 725 AAA GTT GGT GGA AAT CTG GAT TCC AAA GGC TAT GGT GTG GCA ACC CCT 2367 Lys Val Gly Gly Asn Leu Asp Ser Lys Gly Tyr Gly Val Ala Thr Pro 730 735 740 AAA GGC TCA GCA TTA GGA ACG CCT GTA AAC CTT GCA GTA TTG AAA CTC 2415 Lys Gly Ser Ala Leu Gly Thr Pro Val Asn Leu Ala Val Leu Lys Leu 745 750 755 AGT GAA CAA GGC ATC TTA GAC AAG CTG AAA AAC AAA TGG TGG TAC GAT 2463 Ser Glu Gln Gly Ile Leu Asp Lys Leu Lys Asn Lys Trp Trp Tyr Asp 760 765 770 AAG GGG GAA TGT GGA GCC AAG GAC TCC GGG AGT AAG GAC AAG ACC AGC 2511 Lys Gly Glu Cys Gly Ala Lys Asp Ser Gly Ser Lys Asp Lys Thr Ser 775 780 785 GCT CTG AGC CTG AGC AAT GTG GCA GGC GTT TTC TAT ATA CTT GTC GGA 2559 Ala Leu Ser Leu Ser Asn Val Ala Gly Val Phe Tyr Ile Leu Val Gly 790 795 800 805 GGT CTG GGG CTG GCC ATG ATG GTG GCT TTG ATA GAA TTC TGT TAC AAA 2607 Gly Leu Gly Leu Ala Met Met Val Ala Leu Ile Glu Phe Cys Tyr Lys 810 815 820 TCA CGG GCA GAG TCC AAA CGC ATG AAA CTC ACA AAG AAC ACC CAA AAC 2655 Ser Arg Ala Glu Ser Lys Arg Met Lys Leu Thr Lys Asn Thr Gln Asn 825 830 835 TTT AAG CCT GCT CCT GCC ACC AAC ACT CAG AAT TAT GCT ACA TAC AGA 2703 Phe Lys Pro Ala Pro Ala Thr Asn Thr Gln Asn Tyr Ala Thr Tyr Arg 840 845 850 GAA GGC TAC AAC GTG TAT GGA ACA GAG AGT GTT AAG ATC TAGGGATCCC 2752 Glu Gly Tyr Asn Val Tyr Gly Thr Glu Ser Val Lys Ile 855 860 865 TTCCCACTGG AGGCATGTGA TGAGAGGAAA TCACCGAAAA CGTGGCTGCT TCAAGGATCC 2812 TGAGCCAGAT TTCACTCTCC TTGGTGTCGG GCATGACACG AATATTGCTG ATGGTGCAAT 2872 GACCTTTCAA TAGGAAAAAC TGATTTTTTT TTTCCTTCAG TGCCTTATGG AACACTCTGA 2932 GACTCGCGAC AATGCAAACC ATCATTGAAA TCTTTTTGCT TTGCTTGAAA AAAAATAATT 2992 AAAATAAAAA CCAACAAAAA TGGACATGCA TCAAACCCTT GATGTATTAA TATTTATTAT 3052 AGTTTTCATT AGGAATTC 3070 888 amino acids amino acid linear protein 4 Met Gly Gln Ser Val Leu Arg Ala Val Phe Phe Leu Val Leu Gly Leu -22 -20 -15 -10 Leu Gly His Ser His Gly Gly Phe Pro Asn Thr Ile Ser Ile Gly Gly -5 1 5 10 Leu Phe Met Arg Asn Thr Val Gln Glu His Ser Ala Phe Arg Phe Ala 15 20 25 Val Gln Leu Tyr Asn Thr Asn Gln Asn Thr Thr Glu Lys Pro Phe His 30 35 40 Leu Asn Tyr His Val Asp His Leu Asp Ser Ser Asn Ser Phe Ser Val 45 50 55 Thr Asn Ala Phe Cys Ser Gln Phe Ser Arg Gly Val Tyr Ala Ile Phe 60 65 70 Gly Phe Tyr Asp Gln Met Ser Met Asn Thr Leu Thr Ser Phe Cys Gly 75 80 85 90 Ala Leu His Thr Ser Phe Val Thr Pro Ser Phe Pro Thr Asp Ala Asp 95 100 105 Val Gln Phe Val Ile Gln Met Arg Pro Ala Leu Lys Gly Ala Ile Leu 110 115 120 Ser Leu Leu Gly His Tyr Lys Trp Glu Lys Phe Val Tyr Leu Tyr Asp 125 130 135 Thr Glu Arg Gly Phe Ser Ile Leu Gln Ala Ile Met Glu Ala Ala Val 140 145 150 Gln Asn Asn Trp Gln Val Thr Ala Arg Ser Val Gly Asn Ile Lys Asp 155 160 165 170 Val Gln Glu Phe Arg Arg Ile Ile Glu Glu Met Asp Arg Arg Gln Glu 175 180 185 Lys Arg Tyr Leu Ile Asp Cys Glu Val Glu Arg Ile Asn Thr Ile Leu 190 195 200 Glu Gln Val Val Ile Leu Gly Lys His Ser Arg Gly Tyr His Tyr Met 205 210 215 Leu Ala Asn Leu Gly Phe Thr Asp Ile Leu Leu Glu Arg Val Met His 220 225 230 Gly Gly Ala Asn Ile Thr Gly Phe Gln Ile Val Asn Asn Glu Asn Pro 235 240 245 250 Met Val Gln Gln Phe Ile Gln Arg Trp Val Arg Leu Asp Glu Arg Glu 255 260 265 Phe Pro Glu Ala Lys Asn Ala Pro Leu Lys Tyr Thr Ser Ala Leu Thr 270 275 280 His Asp Ala Ile Leu Val Ile Ala Glu Ala Phe Arg Tyr Leu Arg Arg 285 290 295 Gln Arg Val Asp Val Ser Arg Arg Gly Ser Ala Gly Asp Cys Leu Ala 300 305 310 Asn Pro Ala Val Pro Trp Ser Gln Gly Ile Asp Ile Glu Arg Ala Leu 315 320 325 330 Lys Met Val Gln Val Gln Gly Met Thr Gly Asn Ile Gln Phe Asp Thr 335 340 345 Tyr Gly Arg Arg Thr Asn Tyr Thr Ile Asp Val Tyr Glu Met Lys Val 350 355 360 Ser Gly Ser Arg Lys Ala Gly Tyr Trp Asn Glu Tyr Glu Arg Phe Val 365 370 375 Pro Phe Ser Asp Gln Gln Ile Ser Asn Asp Ser Ala Ser Ser Glu Asn 380 385 390 Arg Thr Ile Val Val Thr Thr Ile Leu Glu Ser Pro Tyr Val Met Tyr 395 400 405 410 Lys Lys Asn His Glu Gln Leu Glu Gly Asn Glu Arg Tyr Glu Gly Tyr 415 420 425 Cys Val Asp Leu Ala Tyr Glu Ile Ala Lys His Val Arg Ile Lys Tyr 430 435 440 Lys Leu Ser Ile Val Gly Asp Gly Lys Tyr Gly Ala Arg Asp Pro Glu 445 450 455 Thr Lys Ile Trp Asn Gly Met Val Gly Glu Leu Val Tyr Gly Arg Ala 460 465 470 Asp Ile Ala Val Ala Pro Leu Thr Ile Thr Leu Val Arg Glu Glu Val 475 480 485 490 Ile Asp Phe Ser Lys Pro Leu Met Ser Leu Gly Ile Ser Ile Met Ile 495 500 505 Lys Lys Pro Gln Lys Ser Lys Pro Gly Val Phe Ser Phe Leu Asp Pro 510 515 520 Leu Ala Tyr Glu Ile Trp Met Cys Ile Val Phe Ala Tyr Ile Gly Val 525 530 535 Ser Val Val Leu Phe Leu Val Ser Arg Phe Ser Pro Tyr Glu Trp His 540 545 550 Leu Glu Asp Asn Asn Glu Glu Pro Arg Asp Pro Gln Ser Pro Pro Asp 555 560 565 570 Pro Pro Asn Glu Phe Gly Ile Phe Asn Ser Leu Trp Phe Ser Leu Gly 575 580 585 Ala Phe Met Gln Gln Gly Cys Asp Ile Ser Pro Arg Ser Leu Ser Gly 590 595 600 Arg Ile Val Gly Gly Val Trp Trp Phe Phe Thr Leu Ile Ile Ile Ser 605 610 615 Ser Tyr Thr Ala Asn Leu Ala Ala Phe Leu Thr Val Glu Arg Met Val 620 625 630 Ser Pro Ile Glu Ser Ala Glu Asp Leu Ala Lys Gln Thr Glu Ile Ala 635 640 645 650 Tyr Gly Thr Leu Asp Ser Gly Ser Thr Lys Glu Phe Phe Arg Arg Ser 655 660 665 Lys Ile Ala Val Tyr Glu Lys Met Trp Ser Tyr Met Lys Ser Ala Glu 670 675 680 Pro Ser Val Phe Thr Lys Thr Thr Ala Asp Gly Val Ala Arg Val Arg 685 690 695 Lys Ser Lys Gly Lys Phe Ala Phe Leu Leu Glu Ser Thr Met Asn Glu 700 705 710 Tyr Ile Glu Gln Arg Lys Pro Cys Asp Thr Met Lys Val Gly Gly Asn 715 720 725 730 Leu Asp Ser Lys Gly Tyr Gly Val Ala Thr Pro Lys Gly Ser Ala Leu 735 740 745 Gly Thr Pro Val Asn Leu Ala Val Leu Lys Leu Ser Glu Gln Gly Ile 750 755 760 Leu Asp Lys Leu Lys Asn Lys Trp Trp Tyr Asp Lys Gly Glu Cys Gly 765 770 775 Ala Lys Asp Ser Gly Ser Lys Asp Lys Thr Ser Ala Leu Ser Leu Ser 780 785 790 Asn Val Ala Gly Val Phe Tyr Ile Leu Val Gly Gly Leu Gly Leu Ala 795 800 805 810 Met Met Val Ala Leu Ile Glu Phe Cys Tyr Lys Ser Arg Ala Glu Ser 815 820 825 Lys Arg Met Lys Leu Thr Lys Asn Thr Gln Asn Phe Lys Pro Ala Pro 830 835 840 Ala Thr Asn Thr Gln Asn Tyr Ala Thr Tyr Arg Glu Gly Tyr Asn Val 845 850 855 Tyr Gly Thr Glu Ser Val Lys Ile 860 865 46 amino acids amino acid linear peptide 5 Gly Ser Ala Leu Gly Asn Ala Val Asn Leu Ala Val Leu Lys Leu Asn 1 5 10 15 Glu Gln Gly Leu Leu Asp Lys Leu Lys Asn Lys Trp Trp Tyr Asp Lys 20 25 30 Gly Glu Cys Gly Ser Gly Gly Gly Asp Ser Lys Asp Lys Thr 35 40 45 46 amino acids amino acid linear peptide 6 Gly Ser Ala Leu Gly Thr Pro Val Asn Leu Ala Val Leu Lys Leu Ser 1 5 10 15 Glu Gln Gly Ile Leu Asp Lys Leu Lys Asn Lys Trp Trp Tyr Asp Lys 20 25 30 Gly Glu Cys Gly Ala Lys Asp Ser Gly Ser Lys Asp Lys Thr 35 40 45 40 base pairs nucleic acid single linear Other nucleic acid; Synthetic DNA oligonucleotide 7 ACACTCAGAA TTACGCTACA TACAGAGAAG GCTACAACGT 40 

We claim:
 1. An isolated polynucleotide comprising a nucleic acid sequence which encodes an AMPA-binding human GluR3 receptor selected from the human GluR3A receptor and the human GluR3B receptor, an AMPA-binding fragment thereof, or an AMPA-binding variant thereof.
 29. A human GluR3 receptor selected from the human GluR3A receptor and the human GluR3B receptor, in a form essentially free from other proteins of human origin.
 30. A human GluR3 receptor according to claim 29, which is the human GluR3A receptor.
 31. A human GluR3 receptor according to claim 29, which is the human GluR3B receptor.
 32. An AMPA-binding fragment of a human GluR3 receptor selected from the human GluR3A receptor and the human GluR3B receptor.
 33. (Once Amended) An AMPA-binding fragment of a human GluR3 receptor according to claim 32, which is a fragment of the human GluR3A receptor.
 34. An antibody which binds a human GluR3 receptor selected from the human GluR3A receptor and the human GluR3B receptor.
 35. An antibody according to claim 31, having a reporter molecule coupled thereto.
 36. An antibody according to claim 34, which binds to the human GluR3A receptor.
 37. An antibody according to claim 36, having a reporter molecule coupled thereto.
 38. An immunogenic fragment of a human GluR3 receptor selected from the human GluR3A receptor and the human GluR3B receptor.
 39. An immunogenic fragment according to claim 38, which is an immunogenic fragment of the human GluR3A receptor.
 40. An oligonucleotide which comprises at least about 17 nucleic acids and which hybridizes selectively with a polynucleotide defined in claim
 1. 41. (Once Amended) An oligonucleotide according to claim 1, having a reporter molecule conjugated thereto. 